An electromechanical actuator (FIG. 1) for a valve 110 comprises mechanical means, such as springs 102 and 104, and electromagnetic means, such as electromagnets 106 and 108, for controlling the position of the valve 110 by means of electric signals.
The rod of the valve 110 is applied for this purpose against the rod 112 of a magnetic plate 114 located between the two electromagnets 106 and 108.
When current flows in the coil 109 of the electromagnet 108, the latter is activated and attracts the magnetic plate 114, which comes into contact with it in the so-called “upper” position.
The simultaneous displacement of the rod 112 enables the spring 102 to bring the valve 110 into the closed position, the head of the valve 110 moving against its seat 111 and preventing the exchange of gas between the interior and the exterior of the cylinder 117.
Analogously (not shown), when current flows in the coil 107 of the electromagnet 106 (the electromagnet 108 being deactivated), it is activated and attracts the plate 114, which comes into contact with it and displaces the rod 112, compressing the spring 102, by means of the spring 104, such that this rod 112 acts on the valve 110 and brings the latter into the open position, the head of the valve being moved away from its seat 111 to permit, for example, the admission or the injection of gas into the cylinder 117. The valve is now in the so-called “lower” position.
Thus, the valve 110 and the plate 114 alternate between fixed, so-called switched positions, with transient displacements between these two positions.
The actuator 100 may also be equipped with magnets 118 (electromagnet 108) and 116 (electromagnet 106) intended to reduce the energy necessary to maintain the plate 114 in a switched position, i.e., in contact with one of the electromagnets. Such electromagnets will hereinafter be called electromagnets with a magnet or polarized electromagnets.
The prior-art actuators have the drawback of requiring a considerable amount of energy to maintain the valve in a switched position, even though this maintenance does not supply any propulsion energy for the vehicle.
In addition, they generate a considerable operating noise due to the contact between the plate and the electromagnet.